Development and validation of a quantitative method for the selective determination of tin species in tin octoate by differential pulse polarography.

Tin octoate is used as a catalyst in the synthesis of polydimethylsiloxane (PDMS), a room temperature vulcanizing (RTV) silicone rubber. This rubber is largely used in the medical field due to its great biocompatibility. In this framework, a high-speed and costless analytical method for the determination of stannic ions, Sn(IV), in the presence of stannous ions, Sn(II), has been developed. The separation of these two ions was carried out using differential pulse polarography (DPP). For this purpose, the tin species contents in the catalyst is quantitatively extracted under inert condition to avoid any changes in the ratio Sn(IV)/Sn(II). Polarography showed well-shaped oxidation and reduction peaks respectively at -650 and -860mV for stannous ions. The peak of the stannic ion was well separated and appeared at -1210mV. Many parameters such as extraction process, extraction time, pH, chelating agents and polarographic conditions were optimized. We have also demonstrated that no oxidation of the stannous ions occurred during the sample preparation. The dosing range considered in this study extends between 10 and 40mug/mL, corresponding to 6.8% and 27.2% of the degradation product (Sn(IV)) in the catalyst, regarding to the sampling. Finally this method was successfully validated using the total error concept.

Study of the physicochemical properties in aqueous medium and molecular modeling of tagitinin C/cyclodextrin complexes.

The inclusion complexes of tagitinin C with beta-, 2,6-di-O-methyl-beta- and gamma-cyclodextrin (CyD) was investigated in aqueous medium. The stoichiometric ratios and stability constants (K(f)) which describe the extent of formation of the complexes have been determined by UV spectroscopy and direct current tast polarography (DC(tast)), respectively. For each complex, a 1:1 molar ratio was formed in solution and the trend of stability constants was K(f) (2,6-di-O-methyl-beta-CyD)>K(f) (gamma-CyD)>K(f) (beta-CyD). The effect of molecular encapsulation on the photochemical conversion of tagitinin C was evaluated. No significant protection efficacy was noticed with beta- and gamma-CyD for the complexed drug with the respect to the free one. On the other hand, the photochemical conversion rate was slowed in presence of 2,6-di-O-methyl-beta-CyD. Data from (1)H NMR and ROESY experiments provided a clear evidence of formation of inclusion complexes. The lactone, the ester and the unsaturated ketone parts of tagitinin C inserted into the wide rim of the CyDs torus. These experimental results were confirmed by the molecular modeling using semiempirical Austin Model 1 (AM1) method.

Direct determination of tagitinin C in Tithonia diversifolia leaves by on-line coupling of supercritical carbon dioxide extraction to FT-IR spectroscopy by means of optical fibres.

Supercritical fluid extraction (SFE) with carbon dioxide as extraction medium was on-line coupled to a FT-IR spectrometer equipped with a Mercury Cadmium Telluride (MCT) detector using a tailor-made high-pressure fibre optic flow cell. This method was optimised and developed for the monitoring in real time and the quantification of dynamic extractions of tagitinin C from Tithonia diversifolia leaves. In order to demonstrate the method ability to allow the direct quantification of tagitinin C in the extract medium the standard addition method was used. The area integration of curves obtained by plotting the absorbance of the highly specific C=O stretching vibration at 1668cm(-1) versus time (i.e. extractograms) was used as instrumental response. The SFE/FT-IR process was successfully validated using the accuracy profile as decision tool. On this basis, a linear regression model was chosen for the calibration curve. The relative standard deviation for repeatability and intermediate precision were between 0.8 and 3.1 %, respectively. Moreover, the method was found to be accurate as the two-sided 95% beta-expectation tolerance interval did not exceed the acceptance limits of 85 and 115% on the analytical range investigated (500-2500microg of added amount of tagitinin C). The proposed method allowed the non-destructive extraction of tagitinin C and its on-line quantitative determination in less than 25min thus facilitating the subsequent experiments or the pharmacological studies performed on this compound.

FT-IR measurement of tagitinin C after solvent extraction from Tithonia diversifolia.

Tagitinin C, an antiplasmodial compound, identified as one major compound of the subtropical medicinal plant, Tithonia diversifolia, was determined by FT-IR spectroscopy method. The crude ether extracts from aerial parts of the plant were evaporated to dryness and re-dissolved in tetrachloroethylene (C(2)Cl(4)) before analysis. The magnitude of the absorbance of the very specific CO stretching vibration (nu(CO)) at 1664.8cm(-1) was exploited in order to quantify tagitinin C. The determination coefficient (r(2)) of the calibration scale was 0.9994, the detection limit was lower than 3mugml(-1) and the quantification limit was lower than 10mugml(-1). Recovery values from 100.5 to 101.7% were found for spiked concentration levels from 19.91 to 89.95mugml(-1). The main characteristics of the curves obtained from the calibration standards and from the standard addition technique were not statistically different (Student t-test) suggesting that matrix effects were negligible. The results obtained for the determination of tagitinin C in the crude ether extract from aerial parts of T. diversifolia by LC and FT-IR spectroscopic method agreed well: 0.76+/-0.02 and 0.773+/-0.009, of tagitinin C in dried plant respectively.

Occupational and environmental risk factors of the myelodysplastic syndromes in the North of France.

Aetiological factors of the myelodysplastic syndromes (MDS) are largely unknown, with the exception of alkylating agents, ionizing radiation and benzene. Some other risk factors have been suggested by the few epidemiological studies reported (solvents, ammonia, exhaust gases, metals, pesticides, alcohol). We performed a case-control study to assess the relationship between occupational or environmental factors and MDS. Two hundred and four patients with newly diagnosed MDS, and 204 sex- and age-matched controls were included. Medical history, demographic data, lifetime exposure and hobbies were obtained. Qualitative and quantitative exposure to chemical and physical hazards were evaluated with the patients and reviewed by a group of experts in occupational exposure. The median age was 70 years and 62% of the patients were men. In univariate analyses, we found relationships between MDS and smoking habits, gardening, occupations such as health professionals, technical and sale representatives, machine operators, agricultural workers, textile workers, qualitative occupational exposures (exposed/non-exposed) to oil, solvents, ammonia, pesticides, fertilizers, cereal dusts, contact with poultry or livestock and infective risk, and lifetime cumulative exposure to solvents, oil, textile dust and infective risk. The main risk factors of MDS determined by multivariate analyses (conditional logistic regression) were, being an agricultural worker [odds ratio (OR) = 3.66; 95% confidence interval (CI) 1.9-7.0], textile operator (OR = 3.66; 95% CI 1.9-7.9), health professional (OR = 10.0; 95% CI 2.1-48.7), commercial and technical sale representative (OR = 4.45; 95% CI 1.4-14.6), machine operator (OR = 2.69; 95% CI 1.2-6.0), living next to an industrial plant (OR = 2.45; 95% CI 1.5-4.1), smoking (OR = 1.74; 95% CI 1.1-2.7) and lifetime cumulative exposure to oil (OR = 1.1; 95% CI 1.0-1.2). Further studies should be performed to assess specific exposures more precisely and it would be of interest to develop a map of haematological malignancies according to industrial background.

High stability and high efficiency chemiluminescent acridinium compounds obtained from 9-acridine carboxylic esters of hydroxamic and sulphohydroxamic acids.

A series of hydroxamic acids and sulphohydroxamic acids were prepared and linked to 9-acridinecarboxylic acid through a pseudo-ester function. After N-methylation of the heterocyclic ring, the different compounds were tested for their chemiluminescent properties. Substituents on the hydroxamic functions have shown various effects (steric or electronic) on the luminescence yield or stability of the molecule. The most interesting derivatives were selected in terms of chemical stability and chemiluminescence efficiency. 9-[(N-hydroxysuccinimidyl-4-oxo-4-N-phenylaminobutanoate)N-carb oxylat e]-10-methyl-acridinium (FA6), 9-(N-phenylpivalamide-N-carboxylate)-10-methylacridinium (FA17) and 9-(N-phenylpivalamide N-carboxylate)-10-carboxymethyl-acridinium (FA18) iodomercurates are very promising as chemiluminescent labels. These compounds can be detected at very low levels (10(-16)-10(-17) mol/L) and in our stability evaluation, FA6, FA17 and FA18 showed similar results to the acridinium ester DMAE. Their half-lives at 20 degrees C are greater than 2 weeks.

Chemiluminescence as diagnostic tool. A review.

The principles of chemiluminescence and its applications as diagnostic tool are reviewed. After an introduction to the theoretical aspects of luminescence and energy transfer, the different classes of chemiluminogenic labels including luminol, acridinium compounds, coelenterazine and analogues, dioxetanes, systems based on peroxyoxalic acid and their derivatives are described emphasizing the molecules which best fulfil the requirements of today's clinical chemistry. Applications of chemiluminescence and enhanced chemiluminescence to immunoassays, receptor assays, DNA probes, biosensors and oxygen metabolism are discussed as well as the role of enzymes in the selectivity and the sensitivity of these reactions.

Modeling the exponential growth of filamentous fungi during batch cultivation

In certain conditions, filamentous fungi are observed to grow exponentially during batch submerged growth. It is shown for three cases, with simple mechanistic models, that an exponential growth assumption is reasonable. The basis of these models is the identification of a growth unit, and a mechanism for its doubling with a constant generation time. The importance of the variation of morphological properties within populations is demonstrated by the comparison of computer simulations of simplified models using average values and either experimental data or computer simulations of detailed stochastic models. Copyright 1998 John Wiley & Sons, Inc.

Synthesis of 17 beta-hydroxy esters of 4-estren-17 beta-ol-3-one and carbenicillin, ticarcillin, or functionalized oxacillin: potentially useful conjugates for beta-lactamase-based homogeneous immunoassays.

On the basis of the large range of kinetic constants of their substrates, beta-lactamases seem to be interesting enzymes for the development of homogeneous immunoassays. For this purpose, hapten-penicillin or -cephalosporin conjugates have to be prepared. The aim of this work is to couple the anabolizing steroid nandrolone to several penicillins characterized by extremely low K(m) and kcat values: ticarcillin, carbenicillin, and oxacillin. The easy decarboxylation of derivatives of phenylmalonic acid (carbenicillin) and thienylmalonic acid (ticarcillin) imposes the choice of very mild procedures which have been specifically adapted to each substance investigated. 4-Estren-17 beta-ol-3-one hemiphenylmalonate is conjugated to 6-aminopenicillanic acid after 1,1'-carbonyldiimidazole activation, while 4-estren-17 beta-ol-3-one hemi(3-thiophene)malonate is coupled to 6-aminopenicillanic acid after activation using methanesulfonyl chloride. Before conjugation of oxacillin, a carboxylated analogue of its side chain has been prepared. A procedure resorting to tert-butyl ester protection of the carboxyl group present on the isoxazole ring allows the binding of nandrolone to the remaining carboxyl followed, after specific deprotection, by the conjugation to 6-aminopenicillanic acid giving the oxacillin derivative. In this way, conjugates retaining immunological properties of nandrolone and high inhibiting power of beta-lactamases should be obtained.

Anatomic basis for auditory brainstem implant.

Profound bilateral retrocochlear deafness cannot respond to a cochlear implant. For such patients only electrical stimulation of the cochlear nucleus complex can achieve, at best, a partial restoration of hearing. Based on the experience of the W.F. House group at the House Ear Institute in Los Angeles, we have developed an implantable device with many surface electrodes. A personal study has enabled us to establish the main relationships of the nucleus with the aim of inserting the device in contact with it, and to verify its effectiveness in the region. Histological study of anatomic specimens has shown the presence of spheroid neurone, considered to be the secondary neurone of the auditory pathway, at the level of the area of implantation.

Simulation of growth of a filamentous fungus in 3 dimensions.

The tridimensional growth of a filamentous fungus was simulated, based on a model for the evolution of the microscopic morphology of Trichoderma reesei. When supplemented with a spatial representation of growth, the model correctly simulates the evolution from a single spore to a pellet. Diffusion of oxygen is included in the model. The simulated tridimensional structures have a fractal nature; and the fractal dimension, determined by a box-counting method, increases during growth. The fractal dimension only depends on the mass of the pellet and is not affected by model parameters such as tip extension rate and branching frequency. Realistic pictures are obtained and the radius of the pellet increases at a constant rate. The influence of model parameters (tip extension rate, branching frequency, minimum porosity) on dissolved oxygen concentration profiles, biomass concentration profiles, rate at which the pellet diameter increases, and the evolution of the fractal dimension was determined. The dissolved oxygen profiles were found to be very different from the profiles, obtained by assuming a homogenous biomass distribution within the pellet. Finally, the formation of pellets from spore aggregates is calculated and the size of the spore aggregate is found to only influence the time needed before the appearance of a pellet and not its morphology. (c) 1997 John Wiley & Sons, Inc.

Morphology of Trichoderma reesei QM 9414 in submerged cultures.

The microscopic morphology of Trichoderma reesei QM 9414, growing in submerged culture, was studied by image analysis. The morphology was characterized by the total hyphal length, the total number of tips, the number of actively growing tips, and the length of the main hypha. To describe the growth of a single mycelium a simple model is set-up. The main features of the model are: (1) saturation type kinetics for the tip extension of the individual branches within the mycelium; and (2) random branching with a frequency function, which is proportional to the total hyphal length. The model is used to simulate a population of mycelia, where spore germination is described with a log-normal distribution. From the simulation of the population, the average properties of the mycelia, e.g., the average total hyphal length, are calculated, and by fitting the model to experimental data the model parameters are estimated. Finally, the distribution function with respect to the mycelia properties, that is, number of tips and total hyphal length, is calculated, and it corresponds well with the experimental determination of the distribution function. (c) 1995 John Wiley & Sons Inc.

Clinical efficacy and safety of cefetamet pivoxil in toddlers.

The safety and efficacy of cefetamet pivoxil, an oral cephalosporin of the third generation, have been studied in open, prospective, randomized comparative, clinical trials including 301 toddlers (children aged 1 to 2 years) with upper and lower respiratory tract infections, and urinary tract infections. Cefetamet pivoxil (CAT) syrup formulation was given to 177 toddlers either in the standard dose of 10 mg/kg b.i.d. [n = 116] or 20 mg/kg b.i.d. [n = 61] and 124 toddlers have been treated with comparator drugs [cefaclor, n = 98; phenoxymethylpenicillin, n = 18; amoxicillin plus clavulanic acid; n = 8]. The treatment period was 7 days mainly, except for pharyngotonsillitis for which the treatment duration was 7 or 10 days. The assessment of treatment was based on clinical signs and symptoms primarily in infections of lower respiratory tract and acute otitis media, whereas in patients with pharyngotonsillitis and acute urinary tract infections the bacteriological findings were the main evaluation criteria. The overall therapeutic outcome was successful in 148 (95.4%) of the 155 toddlers to whom CAT was administered and in 87 (85.3%) out of 102 toddlers receiving standard drugs. Adverse events of mild to moderate severity, mainly of gastro-intestinal type (vomiting or diarrhoea) occurred in 14.7% in the patient group receiving CAT, 11.2% in the toddlers receiving the standard dose of CAT, and in 12.9% with the comparator drugs. From the data presented it is concluded that cefetamet pivoxil is efficient and safe in toddlers presenting with community-acquired respiratory and urinary infections mainly caused by S. pneumoniae, H. influenzae, Group A beta-haemolytic streptococci, M. catarrhalis, E. coli, Proteus spp. and K. pneumoniae.

Blood levels of reduced/oxidized glutathione and plasma concentration of ascorbic acid during eccentric and concentric exercises of similar energy cost.

In an attempt to assess the possible oxidative stress associated with the transient exercise-induced activation of polymorphonuclear neutrophils (PMN), we compared the effects of eccentric and concentric exercises (downhill run: DR and uphill walk: UW, respectively) of equal duration (35 min) and similar energy cost (60% VO2max) on plasma levels of ascorbic acid ([AA]) and blood concentration of reduced ([GSH]) and oxidized ([GSSG]) glutathione. Eight healthy male subjects took part in this study. Plasma concentration of myeloperoxidase ([MPO]) was used as a specific marker of PMN activation. While there were no significant changes in [MPO] and [AA] in UW experiments, [MPO] increased (+80%) and [AA] decreased significantly during DR tests (P < 0.01 and P < 0.05, respectively). A significant negative relationship was observed between [AA] and [MPO] in DR experiments only (r = -0.49; P < 0.01). Mean (+/- SEM) basal GSH and GSSG concentrations, calculated by pooling the values measured before both tests, were 0.54 +/- 0.02 and 0.12 +/- 0.007 mM, respectively. The blood concentration of these compounds remained practically unchanged in both exercise tests. These results confirm the role played by the eccentric component of muscle contraction in transient exercise-induced PMN activation and suggest that this activation was partly involved in the decrease in [AA] observed in DR experiments. The oxidant stress associated with the exercise protocol used in this study was insufficient to alter blood levels of reduced and oxidized glutathione.

Infection control in Mississippi dental practices: a comparison of Mississippi Dental Association members and non-members.

In conclusion, the results of the survey were reassuring in many ways. The data indicate that the dental profession in Mississippi seems to have taken advantage of continuing education opportunities, paid increased attention to infection control, and in general, were using appropriate techniques before the OSHA mandate of 1992. Furthermore, members of the MDA not only demonstrated a greater understanding of infections diseases, but were also 20 percent more likely to report behavior known to reduce the risk of cross infection. It will be important to continue to identify the "gaps" and provide information, additional training, and encouragement to the dental profession and to dental auxiliaries to improve infection control procedures where improvement appears to be needed.

Subfemtomole enzyme immunoassay for human growth hormone using affinity chromatography and enzyme amplified detection.

An immunometric assay is described which allows fast detection of attomole amounts of an antigen. The sensitivity is 100 to 1000 times better than that of classical sandwich immunometric assays. Our system allowed the measurement of human growth hormone in the range of 0.1 amol to 100 fmol in a 4-h time period overall. A chromatography column is sequentially filled with two immunoaffinity resins: SP-M1--E1-Ab1 in the upper half and SP-M2--E2-Ab2 in the lower half, where Ab1 and Ab2 represent complementary antibodies reacting with the antigen to be assayed, E1 and E2 represent enzymes, M1 and M2 represent substances reacting reversibly with E1 and E2, respectively, and SP represents the chromatographic solid phase; the sign - represents covalent linkages and the sign--reversible linkages. The sample solution is passed through the column, resulting in binding of the antigen to the first encountered antibody, yielding the immobilized complex SP-M1--E1-Ab1--Ag. The M1 bound is then destabilized by washing with solution of agonist to M1. The freed complex is immediately trapped by the second antibody in the lower part of the column, resulting in the entity SP-M2--E2-Ab2--Ag--Ab1-E1. After a washing step, and amplified detection allows the measurement of the antigen through the activity of the enzyme E1. The antigen-antibody reactions occur in the presence of a very large excess of antibody. The continuous equilibrium displacement due to the chromatographic procedure enhances the yield of complex formation. These factors explain the extremely low levels (subattomole) capable of being detected with this original technique.

[Results of the excision of benign tumors of the liver in 22 patients]. / Résultats de la résection des tumeurs bénignes du foie chez 22 malades.

Between 1979 and 1987, 22 patients underwent resection for a benign liver tumor. A total of 24 tumors were resected: 8 adenomas, 8 focal nodular hyperplasias and 8 hemangiomas. In two patients, focal nodular hyperplasia was associated with hemangioma. Preoperative diagnosis of the nature of the tumor by radiologic investigations (ultrasonography, CT-scan, and selective angiography) was made in only 4 patients (18 p. 100), 3 with hemangioma and one with focal nodular hyperplasia. Ten patients underwent major hepatectomies and 12 had either a segmentectomy (8 patients) or atypical resection (4 patients). Progress in operative management significantly decreased transfusion of packed red cells (p less than 0.05) and that of fresh frozen plasma (p less than 0.02). Ten patients received no blood for fresh frozen plasma. Suppression of abdominal drainage when surgery was uneventful significantly decreased postoperative in-hospital stay (p less than 0.05) to a low 7.8 +/- 0.8 days and improved comfort of patients. These results confirm that preoperative diagnosis of a benign liver tumor is uneasy. They suggest that resection has become a benign procedure in selected surgical centers. The risk of ignoring malignant tumors or leaving a tumor with potential complications should prompt resection when the nature of a liver tumor has not been precisely determined by usual radiologic investigative procedures.

Modification of an ultrasonic scaler for portable use.

To reduce treatment time and muscle fatigue associated with scaling nonambulatory patients at their bedside, a garden sprayer can be adapted to deliver a constant supply of water under pressure to an ultrasonic unit. There have been no significant problems with this arrangement during the 3-year period of use.